Selected exonic sequencing of the AGXT gene provides a genetic diagnosis in 50% of patients with primary hyperoxaluria type 1.

[primary hyperoxaluria type 1]

Definitive diagnosis of primary hyperoxaluria type 1 (PH 1 ) requires analysis of alanine :glyoxylate aminotransferase (AGT ) activity in the liver . We have previously shown that targeted screening for the 3 most common mutations in the AGXT gene (c .33 _34 insC , c .508 G >A , and c .731 T >C ) can provide a molecular diagnosis in 34 .5 % of PH 1 patients , eliminating the need for a liver biopsy . Having reviewed the distribution of all AGXT mutations , we have evaluated a diagnostic strategy that uses selected exon sequencing for the molecular diagnosis of PH 1 .We sequenced exons 1 , 4 , and 7 for 300 biopsy-confirmed PH 1 patients and expressed the identified missense mutations in vitro .Our identification of at least 1 mutation in 224 patients (75 %) and 2 mutations in 149 patients increased the diagnostic sensitivity to 50 %. We detected 29 kinds of sequence changes , 15 of which were novel . Four of these mutations were in exon 1 (c .2 _3 delinsAT , c .30 _32 delCC , c .122 G >A , c .126 delG ), 7 were in exon 4 (c .447 _454 delGCTGCTGT , c .449 T >C , c .473 C >T , c .481 G >A , c .481 G >T , c .497 T >C , c .424 -2 A >G ), and 4 were in exon 7 (c .725 insT , c .737 G >A , c .757 T >C , c .776 + 1 G >A ). The missense changes were associated with severely decreased AGT catalytic activity and negative immunoreactivity when expressed in vitro . Missense mutation c .26 C >A , previously described as a pathological mutation , had activity similar to that of the wild-type enzyme .S elective exon sequencing can allow a definitive diagnosis in 50 % of PH 1 patients . The test offers a rapid turnaround time (15 days ) with minimal risk to the patient . Demonstration of the expression of missense changes is essential to demonstrate pathogenicity .